Realization of room-temperature synthesis of MOFs with trivalent metal ions as coordination centres is a significant challenge for lowering the production cost of MOFs. Herein, a novel strategy of oxidizing radical-promoted facile synthesis of MIL-100(Fe) at room temperature was firstly proposed. The use of benzoquinone as oxidizing radicals successfully promoted room-temperature synthesis of MIL-100(Fe) without HF addition. The resulting RT-MIL-100(Fe) was characterized and its separation performance for recovery of C2H6 and C3H8 from natural gas was examined. RT-MIL-100(Fe) exhibited high BET surface area of 2482 m(2).g(-1), and its adsorption capacities of RT-MIL-100(Fe) for CH4, C2H6 and C3H8 were 0.36, 2.22 and 6.78 mmol.g(-1) at 100 kPa and 298 K, respectively, exhibiting preferable adsorption of C2H6 and C3H8 over CH4. Its IAST-predicted selectivities reached as high as 33.3 and 6.0 for C3H8/CH4 and C2H6/CH4 binary mixtures at 298 K, respectively. The distribution of interaction energy for methane, ethane and propane were simulated using Metropolis method, which is corresponding to the experiment results. Breakthrough experiments confirmed that C1-C3 ternary gas mixtures can be well separated using the fixed bed of RT-MIL-100(Fe) under ambient conditions. RT-MIL-100(Fe) as an iron-based MOFs is very promising for the recovery C2 and C3 from natural gas. More importantly, this novel synthesis technology proposed in this work for room-temperature preparation of MIL-100(Fe) is an energy-saving and environmental friendly methodology.